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Red shift photons: where does the energy come from?

  1. Jan 25, 2010 #1
    The photon energy is given by E = h*f.

    Now, i am aware of the dual wave/particle character of photons. But let's say i emit ONE SINGLE photon, when moving at, say, 0.99c towards the observer. The observer will observe a huge blue shift in this photon. In fact, with respect to the source, it could be in the radio frequency, yet the observer could see a gamma ray because of the blue shift (the 0.99c is just an arbitrary number - i'm sure there's a certain velocity where this case applies).

    So, i'm the observer, at earth, receiving a photon (gamma ray). This is a high energy photon. Yet, when it was emitted, it was a low energy radio wave. Where does this energy come from? The kinetic energy of the source? If so, where does the energy come from in case it was a photon emitted near a black hole and barely managed to escape, with a huge redshift? (okay, energy loss in that case, to overcome the gravity?)
  2. jcsd
  3. Jan 25, 2010 #2
    yes, it's called gravitational redshift.
    http://en.wikipedia.org/wiki/Gravitational_redshift" [Broken]
    Last edited by a moderator: May 4, 2017
  4. Jan 25, 2010 #3
    Thanks a lot Vin !
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